Erosion and Ocean
Waves/Currents
• The student will be expected to
demonstrate an understanding that ocean
waves and currents change coastlines.
• Two categories of coastline we will study:
– Emerging Coastline
– Submerging Coastline
• Submerged Coastline
– This type of coastline results from rising sea
levels and evolves in stages as shown figure
3.6 page 43.
– What were once river valleys have recently
been submerged, producing an indented and
irregular shoreline.
• Emerging Coastline
– Occurs when water deepens rapidly from
shore and land rises steeply upwards.
– It has fairly straight, regular, rocky shore.
– Usually a result from rising land levels.
– Land rebounded after the ice retreated and
melted.
Erosion and Ocean
Waves/Currents
• Erosion of Submerging Coastlines
– In this lesson you will:
• 1.5.1 Define the term spit. (k)
Erosion of Submerging
Coastlines
• Terms Related to Water/ Wave Erosion
– Hydraulic pressure: The pounding force of
water/waves
– Corrosion: Minerals such as calcium carbonate
and limestone dissolve in the water
– Abrasion: rock and sand particles suspended in
the water bump, grind, scrape and gouge
surfaces the water hits.
Long-shore drift terms
• Headlands
• Long-shore drift
• Wave Refraction
• Spit
• Bay Bar
• Bay Beach
Headlands:
• the protrusions of land that extend the
farthest out into wave action.
• The Headland of the
• Eastport Peninsula at Salvage
Long-shore drift:
• refers to the fact that dominant waves
have enough energy to carry silt/sand
from headlands along the shore where it is
later deposited.
Wave Refraction:
• waves bending around headlands as they
hit the shallow water by shore
Spit:
• A ridge of sand running away from the
coast, usually with a curved seaward end.
Spit grows in the prevailing direction of
long-shore drift. Ends are curved by the
action of waves in different directions.
Bay Bar:
• A ridge of mud sand or silt extending
across a bay. Formed when spits stretch
across the mouth of the bay.
Bay Beach:
• An accumulation of sediment deposited
by waves and long-shore drift along the
shore of a bay.
Straightening of an Irregular
Submerging Coastline
• Irregular submerging coastlines have headlands
that protrude out from the shore line.
• The erosion of the headland can deposit silt in
the bay which forms a bay beach as it tends to
reduce the irregularity of the coastline.
• The headland is reduced due to erosion and the
bay is being filled by deposition.
Long-shore drift results in some
sand being deposited parallel to
the shore but connected to the
headland.
These silt deposits are known as
spits.
• Long-shore drift and deposition can
•
continue to the point that the spit closes
off the mouth of the bay.
This extensive deposit is known as a bay
bar.
– As you can see it tremendously reduces the
irregularity in the coastline.
– Continued erosion and deposition can
straighten a coastline over a long period of
time. (Diagram)